Update function description for start_tls_proxy

In [1] the definition of the function was changed, adding the service
name as first parameter. Since this seems to have caused failures in
some plugins, at least update the function template accordingly.

[1] Ifcba410f5969521e8b3d30f02795541c1661f83a

Change-Id: I4d03957f8d3a18625f06379fb21aa7ba55e32797
diff --git a/lib/tls b/lib/tls
index 7bde5e6..b7ad644 100644
--- a/lib/tls
+++ b/lib/tls
@@ -487,7 +487,7 @@
 }
 
 # Starts the TLS proxy for the given IP/ports
-# start_tls_proxy front-host front-port back-host back-port
+# start_tls_proxy service-name front-host front-port back-host back-port
 function start_tls_proxy {
     local b_service="$1-tls-proxy"
     local f_host=$2